Etiology and Management of Limb Dieback of Figs in

California (new project, 2005)

Themis J. Michailides, D. P. Morgan, D. Felts, and H. Reyes

Sharp margins of cankered areas

sporulation

Objectives of project

1. Determine the causal agent(s) of dieback by performing Koch’s postulates.

2. Investigate sources of agent(s) and factors influencing infection of figs.

3. Evaluate susceptibility of fig cultivars to the cause(s) of limb dieback.

4. Develop control methods.

Objective 1: Determine the cause(s) of dieback by performing Koch’s postulates:.

! Isolate suspect agent(s);

! Inoculate figs with suspect agent(s);

! Observe and record symptom development;

! Compare symptoms of inoculations with natural symptoms;

! Re-isolate agent(s) from symptomatic tissues;

! Compare the re-isolated agent(s) with those used for the inoculations.

Samples were collected:

Orchard A• Black Mission

• Calimyrna

Orchard B•Black Mission

(organic & conventional)

•Calimyrna

•Conadria

13.3Phomopsis sp.

78.3Nattrassia mangiferaeCalimyrna

1.0Botryosphaeria rhodina

6.4Fusarium sp.

66.4Phomopsis sp.

26.4Nattrassia mangiferaeMission

Incidence (%)

SpeciesCultivar

Incidence of fungi isolated from limb dieback (Orchard A)

Samples collected on 10 May 2005

Incidence of fungi isolated from limb dieback

6.793.3

N. mangiferaePhomopsis sp.

ConventionalMission 1.7B. rhodina

55.5Phomopsis11.3N. mangiferaeOrganicMission3.3B. rhodina

32.2Phomopsis

65.5N. mangiferaeNorth endCalimyrna

7.87.8

Phomopsis sp.B. rhodina

82.2N. mangiferaeSouth endConadriaIncidence (%)FungusLocationCultivar

Samples collected on 29 June 2005

(Orchard B)

"

"

"

Nattrassia mangiferae

Phomopsis sinerascens

Nattrassia mangiferae

cause of branch wilt

(syn. Hendersonula toruloidea)

Mycelia fragment into spores (arthrospores)

Nattrassia mangiferae pycnidia

arthrosporespycnidiospores

Arthrospores of N.mangiferaefrom culture.

Arthrospores of N. mangiferaedirectly from inner bark of infected branch.

Phomopsis cinerascens

α and β spores

Botryosphaeria rhodina

In Conadria and Calimyrna:

The predominant isolated fungus was Nattrassia mangiferae (Synonym:Hendersonula toruloidea).

In Black Mission:The predominant isolated fungus was Phomopsis cinerascens.

Conclusion

Pathogenicity studies:#Nattrassia mangiferae

#Phomopsis cinerascens

Inoculation of Calimyrna

Inoculation of Calimyrna

Inoculations: (3.5 months later)

Nattrassia:Sunburned: 14.6 mm (46 mm internal streaking)

No sunburned: 11.3 mm (35 mm)

Phomopsis: 8.3 mm (did not grow)

Control7.5 mm

Canker development by Nattrassia mangiferae

Temperature (C)0 5 10 15 20 25 30 35 40

Rad

ial g

row

th (m

m)

0

5

10

15

20

25

Fig (2D3)Almond (65A9) Fig (70D12)

Growth of Nattrassia (1st experiment)

Optimum T (86 – 95°F)

Temperature (C)0 5 10 15 20 25 30 35 40

Rad

ial g

row

th (m

m)

0

5

10

15

20

25

30

35

Fig 2D3 Almond 65A9 Fig 70D12

Growth of Nattrassia (2nd experiment)

Optimum T

Borers can transfer spores

Spread by air, rain, and insects

Branch wilt of walnut

Branch wilt of walnut (Nattrassiamangiferae = Hendersonula toruloidea) and Botryosphaeria dothidea.Similarly, in almonds both fungi present.

Branch wilt of Magnolia

Limb dieback of birch

Madronebranch canker

Hosts of Nattrassia mangiferae (branch wilt, cankers, and dieback)

Blossom blightMango

Branch cankerEucalyptus

Branch wilt Poplar trees

Sudden wiltHevea brasiliensis

Trunk cankerGrapeWilt and diebackFicus bengalensis

Dieback and trunk cankers

Ficus religiosa

Branch wilt (1952)Fig (Ficus carica)

Post-harvest decayOther tropical fruitPost-harvest decayWhite yam, mangoPost-harvest decay Cassava Branch canker Acacia Branch cankerMadrone

Dieback and trunk cankers

GuavaBranch cankerMango Branch cankerEucalyptus Branch wilt Figs (Ficus spp.)Branch wiltCitrus Branch wilt Walnut

Hosts of Nattrassia mangiferae causing branch wilt, cankers, and dieback

Objective 1 (2006): Determine the cause(s) of dieback by performing Koch’s postulates:

! Isolate putative pathogens from multiple samples;

! Inoculate figs with putative pathogens (N. mangiferae, P. cinerascens, & B. rhodina);

Objectives 2006

2. Investigate sources of inoculum and factors influencing infection of figs. (sources in and outside the orchard; effects of wound (=sunburn, mallet, insects, …); effects of temperature; phytotoxins?)

3. Evaluate susceptibility of fig cultivars to the causes of limb dieback. (Calimyrna, Conadria, Black Mission, Brown Turkey, Adams, Sierra, and others?)

4. Develop control methods. (sanitation by pruning; chemical control; biological?)

Effective fungicides against Nattrassiamangiferae that infects toenails

Fluoconazol

Intraconazol

Ketonocazol

Copper-oxychlorite

pyrazophos

fluzilazol

… thus, agric. fungicides such as tebuconazole, propiconazole, …should be tested first.

Slides 37-43 are extra not used in the Fig day 2006 talk.

A B

C D

Nattrassia mangiferae

arthrospores

pycnidia

spores